Conduct acute toxicity studies on retinoids in rats and mice using both oral and IP route exposure. Conduct repeated dose toxicity studies in rats and mice for 28-day periods with daily administration of retinoids by both IP and oral routes. As part of the studies in item 2 above, conduct hematological and chemical chemistry analysis in highest dose groups showing at least 50% survival and in control groups using both sexes and animals treated by each route of exposure. Conduct histopathological examinations on tissues from high and control animals in both sexes, species, and routes. Preserve tissues from remaining animals in 28-day studies for subsequent examinations should such examinations be required. Conduct gross necropsies on all animals in 28-day repeated dose studies.